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Deinonychus claws expalined as climbing adaptions



Erik Omtvedt wrote:
>I don't understand why people want to deny the obvious and make up all of 
>these external excuses for the claw.
        I don't think anyone would seriously suggest that the sickle claw
was not a weapon. The evidence, as compiled by Ostrom, is compelling.

>Evolution would not give a devise for climbing--especially to a 
>large animal--when the animal's main purpose was to hunt the ground 
>feeders.
        Your view exhibits an oversimplistic view of evolution. We have
obseverved time and again that structures which origionally served one
purpose may be modified in decendants to serve other purposes, sometimes to
the exclusion of the origional function. This is called exaptation [sic?].
You don't use your hands as a primary walking organ. You also don't use them
for brachiating.
        Of course, you *can* use them for both. I do not mean to imply that
dromaeosaur claws were not used climbing, but that they did not necessarily
*have* to evolve for killing.

        To head off another argument on this topic: many tree climbing
animals do indeed have more than one climbing claw, in addition to other
adaptations (fingers get longer going out, etc.). It is conceiveable,
however, that our ur-dromaeosaur may have developed this peculiar climbing
adaptation for a number of reasons:
        1) its feet were constrained to a parasagital plane, thus
eliminating the possibility of a sprawling, long fingered, belly-to-the-bark
posture.
        2) it was designed as a runner, and probably needed to maitain some
currency in the track and field event as it developed climbing.
        3) the easiect approach would be to channel some of those powerful
hind limb muscles into the climb...
        4) but, it only had so many toes to work with.
        5) it did, however, have big, powerful arms.
        I envision this early climb wraping its arms around the trunk and
sticking its sickle claws into the trunk like petons, and shimmying up like
a logger. Ever seen loggers do this? they use a chain wrapped all the way
around the tree, and then use their arms to hoist it up, but the basic idea
is similar.

>Besides, what good would a wolf-size predator do in the trees? 
        If the dromaeosaur's ancestors were smaller (and we have no evidence
to say they weren't), would that solve your problem? Think evolution.  As
others have pointed out, large animals can still find uses for trees.
        Of course Dr. Norton and I have our own reasons why we think they
went into the trees...

>Talk about the energy envolved to climb and then what would he do once he 
>got up there?
        Rest, pounce, hide, snuggle, regurgitate, breath, flex and relax
muscles in slow ripples of flesh (sorry, it's that darned liberal arts
degree popping up again), preen, chew on bark, snap at his flying kin, pick
his teeth. The possibilities are endless.

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      Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock TX 79409
      "The cost of living hasn't affected its popularity." - Unknown